On 11/4/2016 12:34 PM, Hal Murray wrote:
[email protected] said:
The only practical way to set the 10811 or 10544 is with a >= 10 turn pot on
the EFC. I never have worked out just why there are so many instruments that
don’t have a pot on the EFC.
How would temperature effect that? For that matter, how does temperature
effect the typical mechanical capacitor? Does anybody play fancy tricks to
cancel out the mechanical motions? (like the mercury pendulum - as the
pendulum rod expands the mercury expands in the other direction to keep the
CG the same)
The variable tuning capacitor in one of the military "frequency meters" (I
forget which one, BC221 leaps to mind) had a small disk on an adjustment screw
that worked against a bi-metallic strip "diving board" to make a temperature
sensitive trimmer capacitor. I suspect, however, that it functioned more to
compensate the inductor than the variable capacitor that was very robust.
Before synthesizers, I built a VFO for a homemade receiver using one of these
cannibalized from a freq meter.
Wes Stewart, N7WS
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